1. Field of the Invention
This invention relates to treatment of contaminants in the environment so that they do not contaminate the liquid in a container, more particularly, a liquid to be used in an assay in an automated clinical analyzer.
2. Discussion of the Art
The members of the ARCHITECT® family of automated clinical analyzers, commercially available from Abbott Laboratories, require fluid handling systems that employ at least one sub-system for aspirating and dispensing samples and reagents, at least one sub-system for dispensing buffers, at least one sub-system for dispensing pre-trigger solutions and trigger solutions, and at least one sub-system for handling liquid waste.
Through aspiration processes, samples are moved from sample containers and assay reagents are moved from reagent containers for dispensing into reaction vessels. In addition, wash buffer is dispensed for priming and flushing. Trigger solutions and pre-trigger solutions are also dispensed into reaction vessels. Trigger solutions and pre-trigger solutions are normally stored on-board the automated clinical analyzers as bulk liquid reagents in relatively large containers.
Liquid reagents are typically aspirated from containers, such as, for example, bottles, and the volume of liquid reagent aspirated is displaced by air from the atmospheric air surrounding the container, through a vent. As a result, carbon dioxide, i.e., CO2, from the atmospheric air surrounding the container is absorbed by and dissolved in the liquid reagent, and the pH of the liquid reagent is lowered. The stability of the liquid reagent when stored upon the automated clinical analyzer is approximately thirty days. Some liquid reagents become unstable after a storage period on an automated clinical analyzer of fewer than thirty days. After thirty days, or less, the amount of carbon dioxide absorbed by and dissolved in the liquid reagent lowers the pH of the liquid reagent to a level that results in adversely affecting results of an assay.
Normally, when liquid reagents are aspirated from a container, the volume of liquid reagent is displaced by atmospheric air surrounding the container, through the actuation of a septum. The septum is also used to minimize evaporation of the liquid reagent. In addition, because the septum is not completely impervious to air, some contamination occurs naturally. As a result, carbon dioxide, or oxygen, from the atmospheric air surrounding the container is absorbed and dissolved in the liquid reagent, thereby affecting the chemical composition of the reagent. For example, when carbon dioxide reacts with water, the pH of the resulting aqueous composition is lowered. Reagent containers can be overfilled with additional liquid reagent to counteract the effects of displacement of liquid reagent by atmospheric air surrounding the container.
FIG. 1 shows a container of the prior art. As shown in FIG. 1, a container 10 has fins 12 for facilitating agitation of the contents of the container 10. A septum 14 is inserted in the mouth 16 of the container 10. The tip 18 of a pipette is inserted through an opening 20 in the septum 14. A liquid reagent 22 is shown in the lower half of the container 10. Displacement air 24 contaminated with a contaminant gas, such as, for example, carbon dioxide, is shown in the upper half of the container 10.
EP 0 766 087 discloses a method for the detection of creatinine in which an aqueous solution containing creatinine is contacted with a dry reagent system containing an indicator for creatinine at a pH above about 11.5. The high pH is provided by a dry alkaline material upon its being hydrated by the aqueous fluid. The dry reagent is packaged with a material capable of absorbing carbon dioxide and at least some ambient water vapor. The carbon dioxide-absorbing material is provided in an amount sufficient to substantially inhibit the formation of carbonic acid in the area of the reagent system. This inhibition of the production of carbonic acid increases the shelf life of the creatinine-detecting device by reducing or eliminating the neutralization of the alkali reagent by carbonic acid formed in situ.
U.S. Pat. No. 6,218,174 discloses degassing by driving a gas-containing solution to sub-atmospheric pressure approximately equal to the solution vapor pressure, and maintaining the subatomic pressure not withstanding evolution of gas from the solution. This method may be accomplished using a vacuum tower arrangement whereby a column of gas-containing liquid is drawn to the maximum physically attainable height. So long as the vacuum is coupled to the liquid column above this height (generally on the order of 34 feet, depending on the ambient temperature and the composition of the liquid), the liquid will not be drawn into the vacuum, which creates a non-equilibrium region of extremely low pressure above the liquid that liberates dissolved gases.
U.S. Pat. No. 7,329,307 discloses a carbon dioxide removal system including a member having a first opening and a second opening to enable air flow and containing lithium hydroxide (LiOH) supported by the member and having an initial water content above an anhydrous level. U.S. Pat. No. 7,329,307 further discloses removal of carbon dioxide by including pre-hydrated LiOH adsorbent in a location having air flow with carbon dioxide. The carbon dioxide is removed with pre-hydrated LiOH adsorbent.
Accordingly, it is desired that the useful life of the liquid reagent be extended as much as possible, so that the entire contents of the container of the liquid reagent can be consumed prior to the date by which it has deteriorated excessively. It is further desired that the liquid reagent have a useful life of at least about thirty days, and preferably longer, after being exposed to atmospheric air surrounding the container. It is still further desired that the pH of the liquid reagent be maintained at the appropriate level for an extended period of time. It is further desired that the effect of contamination of liquid reagents by atmospheric air surrounding the container be reduced so that adverse effects on assay results will be reduced. It is still further desired that the need to overfill reagent containers with additional liquid reagent to counteract the effects of contamination by atmospheric air surrounding the container be eliminated.